Leaving early on a Friday afternoon in June? There's a growing chance your boss has endorsed it.

The percentage of companies that offer some kind of "summer Friday" arrangement -- in which companies officially permit workers, almost entirely office ones, to leave early on Friday afternoons in the summer -- is on the rise. According to a new survey of Fortune 1000 companies by CEB, the Arlington, Va.-based research and consulting firm, 42 percent of companies now officially sanction starting the weekend early, a doubling of the percentage who offered the benefit in 2015, when 21 percent of companies said they did so.

That big jump, says Brian Kropp, who heads the firm's human resources practice, is because the benefit is such a no-brainer for companies to offer. As flexible work arrangements have grown and the average office worker is just a text or phone call away, many people already duck out early on Friday afternoons, especially before long holiday weekends. Making it official gives the company a way to plug their generosity without spending much at all.

"A lot of people already sneak out anyways," Kropp says. "It sends a really positive signal to employees that my company actually cares a little about me, but it's as low cost as you can get."

He says the interest in offering benefits like summer Fridays comes as organizations become flatter hierarchies, with less opportunity for promotion, and as fewer companies offer big raises. Wage growth has remained sluggish even as the economy has improved and the unemployment rate has hit its lowest mark in decades. Unlike higher wages, better benefits are simple to put in and easy to take out if company performance falters, leading more employers to offer a buffet of new perks instead.

"Companies are looking for the alternative mechanisms they can use to engage employees," Kropp said.

CEB's survey asked Fortune 1000 companies whether they offered some kind of "summer Friday" benefit to some employees, and said it could be defined as anything from a short day before the big holiday weekends to getting every Friday afternoon off from late May to early September. More than 220 responded.

Kropp said that while some different companies that answered the survey in 2015 and 2017, their results showed an increase across all industries, and the big size of the jump, versus just seeing the number tick up by a couple of percentage points, gives him confidence that the results aren't simply because of sample changes.

Of course, summer Fridays are hardly a benefit offered to all employees. They're yet another example of the bonus and benefit divide that exists as professional office workers get perks that hourly workers -- who are less likely to get variable pay and often receive less cushy benefits, such as paid leave -- don't. Letting cashiers or production line workers skip out at noon the Friday before Memorial Day just isn't in the cards for most companies. Says Kropp: "This is a perk that is almost exclusively offered to office workers."

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